NATALIE PORTMAN, CHLOE SEVIGNY and KYRA SEDGWICK are joining forces with National Geographic in a new video called "This Bulb" that encourages consumers to switch from incandescent light bulbs to the more eco-friendly compact fluorescent bulbs (CFBs).

In the video -- which features the music of AIMEE MANN and remarkable footage from the National Geographic library -- Natalie, Chloe and Kyra explain how an action as simple as changing a light bulb can help reverse the effects of greenhouse gases.